1. Field of the Invention
This invention relates to an absorbent material for absorbing blood-containing fluids. More particularly, this invention relates to an absorbent material for use in personal care absorbent articles, which are particularly adapted for absorbing various blood-containing bodily fluids while providing comfort and fit to the wearer, such as catamenial articles such as sanitary napkins and pads, wound dressings, and the like. The absorbent material may be a woven material, nonwoven material or a combination of both woven and nonwoven materials.
2. Description of Prior Art
A wide variety of disposable absorbent articles for collecting bodily fluids are known in the art. Commercial absorbent articles include diapers, sanitary napkins, training pants, and incontinent care pads, wound dressings, and the like. Disposable products of this type include some functional elements for receiving, absorbing, and retaining fluids. Typically, such absorbent articles have an absorbent core containing cellulosic fibers, for example, wood pulp fluff, particles of highly absorbent materials, for example, superabsorbents, and an admixture of cellulosic fibers and superabsorbents. Typically, such articles include a fluid-permeable cover sheet or topsheet which typically faces the body of the user, an absorbent core, and a fluid-impermeable backsheet.
Cover sheet materials are utilized for the transport of bodily fluids into the absorbent core of personal care absorbent articles and, thus, materials used for cover sheet applications must manage distinctly different body excretions, depending upon the application and the product type. Some products must manage fluids, such as urine, while others must manage proteinaceous and viscoelastic fluids, such as menstrual discharge and fecal matter. The management of viscoelastic menstrual discharge by feminine care products such as sanitary pads and napkins is exacerbated due to the variations in composition and rheology over a broad range of elasticity. Fluid management in feminine care applications requires control of absorption of bodily fluids, control of fluid retention in the cover, control of stain size and intensity, control of rewet of fluid back to the surface, and control of the release of fluid to the absorbent core.
There are several factors which influence the flow of liquids in fibrous structures including the geometry of the pore structure in the fabrics, the nature of the solid surface (surface energy, surface charge, etc.), the geometry of the solid surface (surface roughness, grooves, etc.), the chemical/physical treatment of the solid surface, and the chemical nature of the fluid. One problem associated with absorbent articles intended for use in handling fluids comprising blood components such as feminine care products and wound dressings is the tendency of red blood cells to block the pores of the materials used for absorption of fluids in such products. Typical of such porous materials are nonwoven or fibrous web materials. The blockage of the pores of the nonwoven or fibrous web materials by the red blood cells results in a reduction in the fluid intake and the wicking capabilities of such products. In addition, in the case of feminine care products such as sanitary pads and napkins, the blockage of pores of nonwoven materials used therein by red blood cells results in increased staining. In the case of feminine care products comprising superabsorbents, the red blood cells attach themselves to the superabsorbents, resulting in blockage of the superabsorbents and a significant reduction in fluid uptake.
In the case of feminine care products such as sanitary pads and napkins, women have come to expect a high level of performance in terms of comfort and fit, retention of fluid, and minimal staining. Of utmost importance, leakage of fluid from the pad onto undergarments is regarded as totally unacceptable.
Improving the performance of feminine care products continues to be a formidable undertaking, although numerous improvements have been made in both their materials and structures. However, solutions addressing the issues arising from the presence of red blood cells in blood or menses in feminine care products, as well as other absorbent materials for handling blood-containing fluids, have not been satisfactorily implemented. It is apparent that a system which effectively handles red blood cells in a manner which addresses the issues set forth hereinabove will not only improve the distribution of incoming fluids by the absorbent material, but will also reduce the tendency toward premature failures of these absorbent articles.
Methods for separating or removing red blood cells from blood-containing fluids generally fall into two categories, agglutination (agglomeration) in which the red blood cells agglomerate, thereby enabling them to be more readily separated from the remaining fluid component, for example, by filtration, and lysing in which the membranes of the red blood cells are disrupted, resulting in a breaking down or breaking apart of the red blood cells. Agglomeration is known to occur, for example, in the presence of certain antibodies. However, we are unaware of any personal care absorbent articles employing these red blood cell management techniques.
Accordingly, it is one object of this invention to provide a blood-containing fluid absorbent material having the capability of reducing the level of red blood cells in the fluid.
It is one object of this invention to provide a feminine care absorbent product having improved fluid handling, including improved fluid intake and wicking, and reduced staining characteristics.
It is another object of this invention to provide a feminine care absorbent product having means for partitioning components of menses, thereby enabling improved fluid handling and reduced staining.
It is another object of this invention to provide a method and system which improves the intake of fluid by superabsorbents which may be present in feminine care absorbent products.
These and other objects of this invention are achieved by a material for absorbing a blood-containing fluid comprising an absorbent material treated with a fluid treatment agent whereby red blood cells within a blood-containing fluid absorbed by the absorbent material are agglomerated or lysed. In accordance with a particularly preferred embodiment, the absorbent material comprises a porous nonwoven web material treated with said fluid treatment agent. In accordance with one embodiment of this invention, the fluid treatment agent is an agglomerating agent which causes the red blood cells in the blood-containing fluid to agglomerate, thereby enabling them to be physically separated from the blood-containing fluid, leaving a fluid that is easier to absorb and less strongly colored. In accordance with another embodiment of this invention, the fluid treatment agent is a cell lysing agent.
The porous nonwoven web material may be produced by any number of means known to those skilled in the art. In accordance with one embodiment of this invention, the nonwoven web material comprises a gradient of pore sizes produced by layering of nonwoven web layers, each layer of which has an average pore size different from the average pore sizes of other nonwoven web layers, forming a porosity gradient nonwoven web material. When disposed between the cover sheet and the liquid impervious backing material of a personal care absorbent article, the porosity gradient nonwoven web material is disposed such that larger average pore sizes are oriented toward the cover sheet and the average pore size of the nonwoven web material decreases in the direction of the liquid impervious backing material. As a result, the porosity gradient nonwoven web material acts as a xe2x80x9cdepth filterxe2x80x9d wherein the agglomerated red blood cells become trapped within the larger size pores of the porosity gradient nonwoven web material. However, care must be taken in selecting the pore size gradient to insure that the fluid separated from the agglomerated red blood cells is still able to pass by trapped particles or clumps of red blood cells, thereby enabling further distribution of the fluid within the personal care absorbent article as desired, for example, to a superabsorbent.
One of the benefits of this invention derives from the fact that the red blood cells of a blood-containing fluid, having come into contact with the fluid treatment agent, are no longer able to block the flow of fluids into the superabsorbents that may be present. This is particularly surprising in the case where the red blood cells are lysed because, unlike agglomerated cells which may become trapped within the pores of the nonwoven material, resulting in their separation from the remaining fluid components, i.e. plasma, the components of the lysed cells remain in the fluid but apparently are no longer able to attach themselves to the superabsorbents.
As used herein, the term xe2x80x9cnonwoven webxe2x80x9d or xe2x80x9cfibrous webxe2x80x9d refers to any material comprising fibrous or fiber-like elements, usually in a random arrangement, joined by bonding points which stabilize the structure, providing at least some mechanical integrity, which form at least some small pores throughout the length and width thereof between adjacent fiber-like elements. The term also includes individual filaments and strands, yams or tows as well as foams and films that have been fibrillated, apertured or otherwise treated to impart fabric-like properties. xe2x80x9cNonwoven websxe2x80x9d or xe2x80x9cfibrous websxe2x80x9d are formed by many processes such as, for example, spunbonding, meltblowing, airlaid and bonded carded processes.
As used herein, the term xe2x80x9cspunbondingxe2x80x9d refers to a process in which small diameter fibers are formed by extruding molten thermoplastic materials as filaments from a plurality of fine, usually circular capillaries of a spinneret with the diameter of the extruded filaments then being rapidly reduced as, for example, described in U.S. Pat. No. 4,340,563 to Appel et al., U.S. Pat. No. 3,692,618 to Dorschner et al., U.S. Pat. No. 3,802,817 to Matsuki et al., U.S. Pat. No. 3,338,992, U.S. Pat. No. 3,341,394 to Kinney, U.S. Pat. No. 3,502,763 to Hartmann, U.S. Pat. No. 3,502,538 to Levy, and U.S. Pat. No. 3,542,615 to Dobo et al. Spunbond fibers are quenched and generally not tacky when they are deposited onto a collecting surface. Spunbond fibers are generally continuous and have average diameters frequently larger than 7 microns, more particularly, between about 10 and 20 microns.
As used herein, the term xe2x80x9cmeltblowingxe2x80x9d refers to a process in which fibers are formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into converging high velocity, usually heated, gas (for example air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface, often while still tacky, to form a web of randomly dispersed meltblown fibers. Such a process is disclosed, for example, by U.S. Pat. No. 3,849,241 to Butin. Meltblown fibers are microfibers which may be continuous or discontinuous and are generally smaller than 10 microns in average diameter.
As used herein, the term xe2x80x9cbonded cardedxe2x80x9d or xe2x80x9cbonded carded websxe2x80x9d refers to nonwoven webs formed by carding processes as are known to those skilled in the art and further described, for example, in U.S. Pat. No. 4,488,928 to Alikhan and Schmidt. Typically, carding processes involve starting with a blend of, for example, staple fibers with bonding fibers or other bonding components in a bulky batt that is combed or otherwise treated to provide a generally uniform basis weight. This web is heated or otherwise treated to activate the adhesive component, resulting in an integrated, usually lofty nonwoven material.
As used herein, the term xe2x80x9cmonocomponentxe2x80x9d fiber refers to a fiber formed from one or more extruders using only one polymer. This is not meant to exclude fibers formed from one polymer to which small amounts of additives have been added for color, anti-static properties, lubrication, hydrophilicity, etc. These additives are generally present in an amount less than about 5 weight percent and more typically about 2 weight percent.
As used herein, the term xe2x80x9cconjugate fibersxe2x80x9d refers to fibers which have been formed from at least two polymers extruded from separate extruders but spun together to form one fiber. Conjugate fibers are also sometimes referred to as multicomponent or bicomponent fibers. The polymers are usually different from each other though conjugate fibers may be monocomponent fibers. The polymers are arranged in substantially constantly positioned distinct zones across a cross-section of the conjugate fibers and extend continuously along the length of the conjugate fibers. The configuration of such a conjugate fiber may be, for example, a sheath/core arrangement in which one polymer is surrounded by another, or may be a side-by-side arrangement, or an xe2x80x9cislands-in-the-seaxe2x80x9d arrangement. Conjugate fibers are taught, for example, by U.S. Pat. No. 5,108,820 to Kaneko et al., U.S. Pat. No. 5,336,552 to Strack et al., and U.S. Pat. No. 5,382,400 to Pike et al. For two component fibers, the polymers may be present in ratios of 75/25, 50/50, 25/75, or any other desired ratios.
As used herein, the term xe2x80x9cbiconstituent fibersxe2x80x9d refers to fibers which have been formed from at least two polymers extruded from the same extruder as a blend. Biconstituent fibers do not have the various polymer components arranged in relatively constantly positioned distinct zones across the cross-sectional area of the fiber and the various polymers are usually not continuous along the entire length of the fiber, instead usually forming fibrils or protofibrils which start and end at random. Biconstituent fibers are sometimes also referred to as multiconstituent fibers. Fibers of this general type are discussed in, for example, U.S. Pat. No. 5,108,827 to Gessner.
As used herein, the term xe2x80x9cpolymerxe2x80x9d generally includes, but is not limited to, homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc., and blends and modifications thereof. In addition, unless otherwise specifically limited, the term xe2x80x9cpolymerxe2x80x9d includes all possible geometric configurations of the material. The configurations include, but are not limited to, isotactic, syndiotactic, and random symmetries.
As used herein, the term xe2x80x9cabsorbent materialxe2x80x9d refers to any material having fluid absorption properties.
As used herein, the term xe2x80x9cpersonal care absorbent articlesxe2x80x9d refers to diapers, training pants, absorbent underpants, adult incontinence products, sanitary wipes and feminine hygiene products such as sanitary napkins and pads.
As used herein, the term xe2x80x9cintakexe2x80x9d refers to the ability of an absorbent article to absorb fluid. Intake time is used to assess the quality of absorption with lower intake times denoting materials capable of rapid absorption and higher intake times denoting materials with poorer absorption.
As used herein, the term xe2x80x9cstainxe2x80x9d refers to fluid, wet or dry, which is present on the top surface, in, or on the bottom surface of a cover material or topsheet of a personal care absorbent article.
As used herein, the term xe2x80x9cgradient porosityxe2x80x9d refers to a porous system in which the average pore size in the system decreases (or increases) from one side of the system to the opposite side of the system. In the case of personal care absorbent articles employing porosity gradient nonwoven web materials in accordance with this invention, average pore sizes decrease from the side of the nonwoven web material disposed towards the topsheet or cover of the absorbent article in the direction of the liquid impervious backsheet.
This invention, in accordance with one embodiment, provides a nonwoven web material suitable for use in personal care absorbent articles such as sanitary pads, napkins and tampons, wound dressings and the like, the intended purpose of which is to absorb and store blood-containing fluids. The nonwoven web material of this invention reduces the impact of red blood cells on fluid intake, wicking capabilities, and staining. The nonwoven web material of this invention is a porous material which is treated with a fluid treatment agent whereby the red blood cells in a blood-containing fluid, such as menses, are either agglomerated or lysed.
In accordance with one preferred embodiment of this invention, the average pore size of the pores of the nonwoven web material is in the range of about 10 microns to about 200 microns, thereby ensuring that the individual red blood cells will be able to pass through the outermost pores of the nonwoven web material into the interior thereof while also ensuring that the agglomerated red blood cells will be unable to pass through the pores to contact superabsorbents which my be present.
The porsous nonwoven web material of this invention may be produced by any method known to those skilled in the art for producing nonwoven web materials. The fibers from which the nonwoven web material of this invention is made may be produced, for example, by meltblowing or spunbonding processes, including those processes producing bicomponent, biconstituent or polymer blend fibers which are well known in the art. These processes generally use an extruder to supply melted thermoplastic polymer to a spinneret where the polymer is fiberized to yield fibers which may be staple length or longer. The fibers are then drawn, usually pneumatically, and deposited on a moving foraminous map or belt to form the nonwoven fabric. The fibers produced in the spunbond and meltblown processes are microfibers.
Alternatively, the nonwoven web may be a bonded carded web. Bonded carded webs are made from staple fibers, which are usually purchased in bales. The bales are placed in a picker, which separates the fibers. Then, the fibers are sent through a combing or carding unit, which further breaks apart and aligns the staple fibers in the machine direction to form generally machine direction-oriented fibrous nonwoven web. Once the web is formed, it is then bonded by one or more of several known bonding methods. One such bonding method is powder bonding wherein a powdered adhesive is distributed through the web and then activated, usually by heating the web and adhesive with hot air. Another suitable bonding method is pattern bonding wherein heated calendar rolls or ultrasonic bonding equipment are used to bond the fibers together, usually in localized bond pattern, though the web can be bonded across its entire surface, if so desired. Another suitable bonding method, particularly when using bicomponent staple fibers, is through-air bonding.
In accordance with one preferred embodiment of this invention, the nonwoven web material of this invention is a multilayer laminate in which nonwoven web material layers having different average pore sizes are layered on e upon another so as produce a nonwoven web material having a porosity gradient as defined hereinabove.
To provide separation of the red blood cells from the blood-containing fluids absorbed into the personal care absorbent article in accordance with one embodiment of this invention, the porous nonwoven web material is treated with a fluid treatment agent which is an agglomerating agent which causes the red blood cells to clump upon coming into contact with the agglomerating agent. Suitable agglomerating fluid treatment agents for use in the personal care absorbent article of this invention include, but are not limited to, antibodies, polycationic materials, that is highly positively charged polymers, and tri-block copolymers of polypropylene oxide and polyethylene oxide. One particularly suitable tri-block copolymer goes under the commercial name of PLURONIC(copyright) F-98 available from BASF (Germany) and constitutes a particularly preferred embodiment of the invention. PLURONIC F-98 is a tri-block copolymer surfactant of 80% by weight polyethylene oxide and 20% by weight polypropylene oxide having a molecular weight of about 9000.
Investigations which we have conducted have shown that greater than about a 1% by weight PLURONIC F-98 solution is required to agglomerate red blood cells in blood and menses. In accordance with a particularly preferred embodiment of this invention, the agglomerating fluid treatment agent is a 2% by weight solution of PLURONIC F-98.